1. Field of the Invention
The present invention generally provides hydraulic binders based on blast furnace slag and clinker or Portland cement (slag cement) presenting mechanical strengths (compression) after 2 days of at least 8 Mpa and preferably meeting the 32.5 R, 42.5N, or 42.5 R classes according to the EN 197-1 standard, as well as mortars and concretes obtained using such hydraulic binders.
2. Description of Related Art
The development of use of blast furnace slag as a substitution to clinker or Portland cement (slag cement) notably to reduce the CO2 released in the atmosphere per ton of binder, represents a great economic stake for the future. However, the use of slag cement, generally induces obtaining low early mechanical strengths, all the more so when the content of blast furnace slag is high and the temperature is low, and it poses performance regularity problems.
On the other hand, the mechanical strengths obtained after 28 days are generally sufficient. To palliate these insufficient early mechanical strengths accelerating additives are commonly used, notably calcium salts or alkali, sodium or potassium salts such as chlorides, nitrates, nitrites, formates, thiocyanates.
These accelerating additives are used:                either at the concrete batching plant level (concrete application), as admixtures, where it is possible to directly use a cement of the CEM III A or B type, or make in situ a mixture of Portland cement+slag, at the mixer stage.        or at the cement plant level (cement plant application), where they are mixed with the clinker+slag during the production of the slag cement.        
The accelerating additives used until today give irregular performances with the slag cements, which vary notably depending on the type of cement, of the batch of cement and of the application temperature. In certain cases, their impact even results in a loss of mechanical strengths at the early ages contrary to what is sought after.
In particular the calcium and sodium chlorides are considered as the best performing accelerators for the slag cements, but they have a very harmful effect in terms of reinforcement corrosion.